If you have any sort of way to ask a bunch of people about their experiences and impressions of circuses, you might get a lot of useful answers.
I remember a circus used to visit Cape May, New Jersey, each summer. I remember one time wandering through the menagerie and watching a few rather small elephants eating. Elephants have to eat almost constantly. I'm sure that each of the elephants would have had a chain around an ankle attached to a stake in the ground.
I don't remember what I was thinking about at the time. But another childhood experience I had was going to some party at a place in the country. There was sheep with a chain around its neck attached to a stake in the ground and the sheep was probably used as a living lawn mower.
The sheep pulled on the chain and pulled it off the stake or pulled the stake out of the ground. My sister and I ran to the man of the house and told him and he went and pulled on the chain to pull the sheep back where it belonged. And I was surprised by what a struggle it was for the man to pull the sheep.
So I suppose that a child like me, watching the circus elephants placidly eating, could have remembered a sheep that got loose and imaged how much stronger the elephants were than the sheep, and thought that if the circus elephants wanted to they could probably pull up their stakes with ease and wander off.
I think that many people constantly compare present situations with past ones.
For example, in a circus, a customer could remember being scratched by a kitten and compare the claws of the big cats to those of the kitten.
Or they could wonder how similar the personalities of the big cats are to those of house cats they knew.
Or they could compare their own klutziness to the skills of the acrobats.
And if people go to the circus together with friends and family, they might discuss such things.
And if your story involves mistreated circus animals, the characters might wonder how content they are and if they might try to escape today and how easy would it be for them.
And maybe if you ask a hundred people or so for their memories of the circus you can get enough information for your story.
And there are no doubt many websites about circuses.